Generator of time-spaced pulse signals of varying duration



May 15, 195.1 n. E. suNs'rElN 2,553,284

GENERATOR 0F TIME-SPACED PULSE SIGNALS OF VARYING DURATION Original Filed Dec. 24, 1947 Patented May 15, 1951 GENERATOR OF TIME-SPACED PULSE SIGNALS OF VARYING DURATION David E. Sunstein, `Cynwyd, Pa., assignor to Philco Corporation, Philadelphia, Pa., a corporation of Pennsylvania vContinuation of applications Serial No. 793,742, December 24, 1947, and Serial No. 34,881, June 24, 1948. This application March 17, 1949, Se-

rial No. 81,888

8 Claims. l

The invention herein described and claimed relates to novel and improved means for generating time-spaced electrical pulse signals of varying duration, and in particular to such means in which the durations of successively generated pulse signals are determined in response to the instantaneous value of a predetermined characteristic of a control signal which varies as a function of time. More particularly, the invention contemplates varying the durations of the generated pulses in a random manner in response to a control signal having a characteristic which varies randomly with time. In the latter instance the invention is particularly adapted for use in radar systems where it is desired to transmit pulses of high frequency energy of randomly varying duration in an endeavor to minimize the deleterious effects of hostile countermeasures. Such a radar system, employing the present invention, is described in my copending application Serial No. 34,881, filed June 24, 1948, for Variable Duration Pulse Radar System, my present application being a continuation of said application and of application Serial No. 793,742, led December 24, 1947, for Electrical System, said latter application having since been abandoned. However, it is to be understood that the present invention is not limited to this application but is generally usable Wherever it may be desired to generate timespaced pulses of duration which varies either randomly or in accordance with a predetermined function of time. Thus, for example, the invention is applicable in a duration-modulated pulse communication system.

Accordingly the principal object of the invention is to provide novel and improved means for generating time-spaced electrical pulse signals oi varying duration.

Another object of the invention is to provide means for generating time-spaced electrical pulse signals of varying duration and whose durations are determined in accordance with the instantaneous value of a predetermined characteristic of a time-varying control signal at successive instants of time.

Still another object of the invention is to provide means for generating time-spaced electrical pulse signals whose durations vary in a random manner.

The invention will be described with reference to a representative embodiment thereof suitable for generating time-spaced pulse signals whose durations vary randomly. The single drawing accompanying this specification is a schematic diagram of such an embodiment.

(Cl. Z50-27) Referring to the gure, rectangular wave generator It may be any suitable generator of recurrent pulses !8, which pulses are preferably of substantially rectangular wave-form and may be of relatively long duration compared to their spacing. These pulses are differentiated in a circuit comprising condenser 29 and resistor 2l to produce appreciably shorter duration pulses 22 timed by the leading and trailing edges of pulses i3. The negative pulses resulting from differentiation are selected by diode 23 and applied to the grid of amplifier tube 25, in the output circuit of which is connected a differentiating inductor 26. The latter differentiates the narrow negative pulses All to yield closely spaced positive and negative pips or pulses 2l corresponding respectively to the falling and rising portions of pulses ll. The positive pips, applied through connection 28 to the grids of tubes 29 and 39, cause these tubes to conduct. Tubes 2e and 3a, the plate-cathode circuits of which are connected in series, constitute a noise gate in the form of a conventional clamping circuit Well known in the art and frequently used in radar systems. A signal of randomly varying amplitude, from a noise generator comprising plate current saturated vacuum tube 98 and associated circuits, is amplified in amplifier S9 and supplied to the plate of tube 29. When tubes 25 and 3b are caused to conduct in response to a positive impulse applied to their grids through connection 28, condenser 3|, connecting the cathode of tube 29 and the plate of tube 38 to ground, will commence to discharge through tube 39. However, at the same time, it will lcommence to be charged through tube 29 to a new potential determined by the instantaneous value of the amplitude of the noise signal applied to the plate of tube 29 at the instant that tube 29 is conducting. The iinal potential assumed by condenser 3l at the end of the conducting period of tubes 29 and 39 will, except as modiiied by stray leakage, remain substantially constant until tubes 29 and B are again caused to conduct and re-establish the potential of condenser 3| in accordance With a later instantaneous value of the noise signal from amplier 32. During these intervals the potential across condenser 3! is applied to the grids of tubes 32-35, connected respectively in the cathode circuits of tubes 38- 39. Tubes 32-39 cooperate with condenser-s l- 44, connected as shown, to provide a multisection variable delay line, the delay of which is determined by the potential applied to the grids Y of tubes 32-35 from condenser 3l. This delay line comprises, in effect, a plurality of cascaded RC sections, each consisting of one of the condensers lll- 44 and a fraction of the plate impedance of the triode, to the cathode of which one of the condenser plates is. connected. rIhis fraction is determined by the mutual' conductance of the triode, and its magnitude is variable in response to variations in the plate current in the triode. The latter is, in turn, controllable. throughout a relatively Wide rangethrough the;- medium of a second triode connected in the cathode circuit of the rst. Thus', or example, the delay of the section comprising tubes 33 and 37 and condenser 42 Will vary as the potential of the grid of tube 33 is varied. Varying the-po-A tentials of the grids of each4 oi tubesi%'-3:T` in' unison in the same sense will' yield" a cumulative" delay of appreciable and varying magnitude throughout the several sections of the delayline. This arrangement, Well known in the art, is

fullyv described in copending; application ofl Millard E. Ames, Jr., Serial Number 563,699, iiled November 16, 1944, now Patent No. 2,505,329, issued May 2, l95and assigned to Philco Corporation, vvhich application also describes other equivalents Which may be.A substituted for the specific delay. line` here shown.

Thus it will be seen tha-tithe delay o thevariable delay lineis established by the potential across condenser 3|-, which, in turn, is periodi.- cally re-estabiished to a random value determined by the instantaneousvalue of a noise signal at the time of occurrence of the positive pips of Wave-form 2l, and is maintained at this value until the occurrence of a subsequent positive pip. The negative pips of the Wave-form 2l developed across inductor 28 are selected through the action of diode lil and are applied to the grid of tube M3, which, together' with tube andv asso-- ciated'connections, forms aconventional Eccles- Jordan trigger circuit, Whichisso well knovin as not to requirei further description. The negative pulses applied to the grid of tube 48 Will cut it off, and at the same. time will cause tube d to commence conducting. It Will be noted that this actuation of the trigger circuit-occursl just after the redetermination of the delay of the variable delay line by the potential' acrosscondenser 3| in response to a positive pip of wave-form 2. Negative impulses causedY to appear on the plate of tube 49 are supplied through connection 5t to the variable delay line.` Delayed negative impulses from theoutput of the delay line are in.- verted in inverter tube 5i andr appliedY through connection 52 tothe grid ofl tube 48 of thetrigger circuit to cause it again to conduct. trigger circuit is caused to generate negative pulses 54 which appear oni the plate` of tube t5 and which vary in` duration depending upon the amount of delay introduced bythe variable'delay line. tion are availablev for'supply' through' connection 53 to any desired utilizaticndevice.

As mentioned in the# preceding' paragraph, when tube 133 is rendered non-conductivefin re'- sponse to the negative pip applied to its grid from diode 4l, tube-39 will commence to conduct, and the decreaseiin potential oftheaplate'of that tube Will be transmitted' through they variable delay line, inverter tube 5|- and connection-de to the grid of tube 43, Where it will. appear as a delayed increase in potential whichrwill operate to render tube ed again conductive and tube dit non-conductive; Similarly, when this occurs, the plate potential of 'tube 49 Willl'risef this. change. in potentialwill bevapplied to the.' input Thus the it These pulses of randomly varying dura- 4 of the delay line. In the absence of diode |06, included in connection 52 from the output of inverter tube 5| to the grid of tube 48 in the trigger circuit, and1 so poled asi to permit only impulses of'positive polarity from tube 5| to be applied to the grid of tube 48, a corresponding negative impulse would subsequently be applied to the grid of tube t'ocause it to cut off. If, as will generallyv be. the case, the variation in the amount of delay introduced by the variable delay f mined by the magnitude of thedelayin the vari.-

ablel delay line, and there wouldbeproduce'd-at the plate of tubed; a series. of f pulses. of equal duration and spaced by intervals equal. to. their. durations, insteadY of a single pulse. of: relativelyy short duration initiated in response; to each; of: the triggering, pips supplied throughdode il?V to the grid of tube 48:.. The; inclusion inconnection of diode H39, or some similar unilaterally conductive device, appropriately` poled,V eliminates. this difficulty by permitting the applicationy to. the .grid of tube Q3from:,the:plate of. tube 51|., oil pulses of but a single4 polarity. Thus. when tube, dii has once; been rendered conductive. in response; to a delayed and; inverted negative impulse fromy the plate of tube 49;,itfwill: not again be rendered non-conductive untilthe subsequent application to its grid of a negative triggering. Dip through diode 41. It will be noted also that preferably there is provided a D. C; connection, through a resistor |i| of suitable value, from the plate ofi diode IBG to ground; 'Ihis is tov permit. dissi-- pation of negative charge which otherwisev would' accumulate on coupling condenser. |52, in re.- sponse to the, negative pips applied to the. Igridofj tube 48, andwhichwould tend to render diode; |09 ineffectual to pass positive impulses from tube 5| to the grid of tubefll'.v

It will, of course, be understood that the irr- Vention is susceptibleof embodiment in forms: other than the one here describedby way of. example, and for purposes other than therone` here: specifically mentioned, and:r that; accordingly the,A invention is subjectk onlyl to those limitations expressed in the appendedY claims.

1. In a, generator of time-spacedi'pulse signals cf varying duration, a source of*v time-spaced pulse signals, a pulse generator supplied with pulse sig.-` nals from said source and responsive theretoeto initiate the generation of said varying durationpulses, means responsive-to the initiationsl of: saidt varying duration: pulses; for producing pulses variably delayed with reference-to saidinitiations, means responsiveto pulses from. said sourcey for altering said delay,1and means.Y for applying. said' delayed pulses to said pulse generator toterminate said varying duration pulses.

2. In a generator ofgtime-spacedl pulse signals of varying duration, a sourcerof time-spacedpulse signals, a pulse generatorsupplied with pulsevsig.- nais from said source and responsive. theretoy to. initiate the generationgof." saidvarying duration: pulses, said generator' being controllable tovaiy the durations of pulses generated thereby, means responsive to the initiations of said varying duration pulses for producing pulses variably delayed with reference to said initiations, means responsive to pulses from said source for altering said delay, and means for applying said delayed pulses to said pulse generator to control the durations of the pulses generated thereby.

3. In a generator of time-spaced pulse signals of Varying duration, a source of time-spaced pulse signals, a source of a signal of Varying characteristic, a pulse generator supplied Avvith pulse signals from said rst source and responsive thereto to initiate the generation of said varying duration pulses, means responsive to the initiations oi said Varying duration pulses for producing pulses variably delayed With reference to said initiations, means responsive to pulse signals from said first source and to said signal of varying characteristic from said second source for controlling said delay, and means for applying said delayed pulses to said pulse generator to terminate said varying duration pulses.

4. In a generator of time-spaced pulse signals of varying duration, a source of time-spaced pulse signals, a pulse generator supplied With pulse signals from said source and responsive thereto to initiate the generation of said Varying duration pulses, means responsive to the initiations of said Varying duration pulses for producing pulses variably delayed with reference to said initiations, said last-named means being controllable in respense to a potential applied thereto to determine the amount of said delay, means for applying a potential to said last-named means to determine said delay, a source of a signal of varying characteristic, means responsive to pulse signals from said source for redetermining the value of said potential applied to said delay device in accordance with the values of said Varying characteristic upon the occurrence of said pulse signals from said source, and means for applying said delayed pulses to said pulse generator to terminate said varying duration pulses.

5. In a generator of time-spaced pulse signals of varying duration, a source of time-spaced pulse signals, a pulse generator supplied with pulse signals from said source and responsive thereto to initiate the generation of said varying duration pulses, means responsive to the initiations of said varying duration pulses for producing pulses variably delayed With reference to said initiations, said last-named means being controllable in response to a potential applied thereto to determine the amount of said delay, means including :a condenser for developing a potential and for applying said potential to said last-named means to determine said delay, ra source of a signal of varying characteristic, means supplied with said signal and with pulse signals from said rst-named source, said last-named means being responsive to said pulse signals to redetermine the potential upon said condenser in accordance with the values of said varying characteristic upon the occurrence of said pulse signals, and means for applying said delayed pulses to said pulse generator to terminate said varying duration pulses.

6. In a generator of time-spaced pulse signals of varying duration, a source of time-spaced pulse signals of substantially equal duration, a pulse generator responsive to the trailing edges of said last-named pulse signals for initiating the generation of said varying pulse signals, said generator being controllable to vary the durations of pulses generated thereby, a source of a signal, a characteristic of which varies, and means supplied 'With said last-named signal and With pulses from said first-named source for controlling said generator to determine the duration of each generated pulse initiated in response to the trailing edge of a pulse from said first-named source in accordance with the value of said varying characteristic upon the occurrence of the leading edge of said last-named pulse.

'7. In a generator of time-spaced pulse signals of varying duration, a source of time-spaced pulse signals of substantially equal duration, a, source of a signal of Varying characteristic, a pulse generator responsive to the trailing edges of pulses from said iirst-named source to initiate the generation of said varying duration pulses, means responsive to the initiations of said varying dunation pulses for producing pulses variably delayed with reference to said initiations, means responsive to pulse signals from said first-named source and to said signal of varying characteristic from said second source for controlling said delay in accordance with the values of said varying characteristic upon the occurrence oi the leading edges of pulses from said rst-named source, and means for applying said delayed pulses to said pulse generator to terminate said varying duration pulses.

8. Apparatus according to claim 3, in which said source of a signal of varying characteristic comprises a Vacuum tube having at least triode elements and means for applying to said tube a plate voltage of sucient magnitude to operate said tube at plate current saturation, whereby the plate current of said tube is caused to Vary in a random manner.

DAVID E. SUNSTEIN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,405,876 Crosby Aug. 13, 1946 2,433,667 Hollingsworth Dec. 30, 1947 2,462,100 Hollabaugh Feb. 22, 1949 

